Stone polishing wheel for contoured surfaces



J. J. BOUVIER 3,517,466

STONE POLISHING WHEEL FOR CONTOURED SURFACES June 30, 1970 Filed July 18, 1969 INVENTOR Jean flour/er ATTORNEY United States Patent Olhce 3,517,466 Patented June 30, 1970 3,517,466 STONE POLISHING WHEEL FOR CONIOURED SURFACES Jean J. Bouvier, T onawanda, N.Y., assignor to Ferro Corporation, Cleveland, Ohio, a corporation of Ohio Continuation-impart of application Ser. No. 725,649, May 1, 1968. This application July 18, 1969, Ser. No. 846,649

Int. Cl. B24d 17/00 11.5. CI. 51-358 5 Claims ABSTRACT OF THE DISCLOSURE Cylinders carrying an abrasive bonded to one end thereof and fixed to a flexible disk which is in turn fixed to a compressible elastomer disk, which in turn is fixed to a rigid rotatable driving plate, to form an abrasive polishing wheel for stone adaptable to polish contoured surfaces. In a preferred embodiment, the driving plate is tapered downward to impart a slanted workface and cut more smoothly.

This application is a continuation-in-part of US. Ser. No. 725,649 filed May 1, 1968, now abandoned.

This invention relates to an abrasive device intended for polishing the face of blocks of granite, marble or the like for use as monuments, corner stones, etc. particularly where curved contoured surfaces are to be polished. In prior practice this has been accomplished using relatively large blocks of diamond impregnated metal bolted to supporting disks of steel or nylon which were to a small degree flexible but far more rigid than my device and as a result were very diflicult to conform to irregular surfaces and frequently left serious scratches in the surface being polished.

The device of the present invention is considered to be somewhat superior to the one described in my copending application Ser. No. 640,686 filed on May 23, 1967, since issued, on Sept. 2, 1969 into US. Pat. 3,464,166, in which there is employed a series of springs to separate a thin flexible face plate carrying abrasive from a rigid backing drive member. While superior to earlier polishing wheels, that device in use does not develop as uniform a facial curvature as the present one, but rather forms a some what undulating face which is depressed somewhat more deeply between the supporting spring areas than it is immediately over these areas. I find that for really fine work the instant device requires less critical attention by the operator to obtain a superior polish.

In the present device, small abrasive cylinders from We to inch in diameter (usually 4 inch) are made from powdered metal with grains of diamond or other abrasive material embedded therein at the substantially fiat, abrading ends thereof. The opposite ends thereof are cemented in place in holes in the surface of a flexible disk of any suitable, conventional, material well known in the art. This disk is cemented in turn to a readily compressible pad of elastomer material which in turn is cemented to a rotatable steel plate which drives the entire assembly.

The construction of this device and its method of manufacture will be clearly understood by reference to the accompanying drawings in which:

FIG. 1 is a view of the working face of my device;

FIG. 2 is a fragmentary cross section along line 2-2 of FIG. 1, showing detail of the assembly of a cylinder and the various backing layers; and

FIG. 3 is a stylized sectional view of a cross section of one of my devices in use where it is pressed against a concave section of a stone being polished to illustrate the deformation of my device to coincide with the curvature of the piece being worked on.

Referring to the various figures, especially FIG. 2, 1 designates the cylindrical, abrasive-faced studs. These are prepared using methods well known in the art. They may be molded in a barrel type mold which may be of steel or of graphite. Into the barrel of the mold I place a measured or weighed quantity of my abrasive mix 2 comprising for example 5 to 10% by volume of sized diamond grits and from O to 25% by volume of other abrasive such as crushed boron carbide. The remainder consists of powdered metals. An excellent product is made using 10% tin and copper though these proportions may be varied from 5 to 15% tin in order to give a softer or harder acting abrasive body or other powdered metals familiar in this art may be used. mesh or finer powdered metal should be used.

As will be apparent the foregoing mixture may be varied to accomplish various types of polished finishes.

On top of the abrasive mix in the mold I place an additional amount of abrasive-free powdered metal 3 to form the base of the stud for insertion in the flexible disk. The metal and abrasive in the barrel is then covered with a steel plunger and the entire assembly of mold, mix and plunger heated at a temperature from 1500 F. to 1900 F. after which it is quickly placed in a press and the mixture compressed under the plunger using a pressure of 3 to 5 tons per square inch while still hot. The mold is then cooled to room temperature and the finished stud removed.

The mold and plunger may be made of 25-20 nickel chromium steel which has adequate strength and is not harmed by the high temperature used. If a graphite mold is used, pressure of 10 to 50 psi. should be applied but the operation is otherwise similar.

For studs intended for preliminary and relatively rough work diamonds of 25 to 35 mesh to the inch are used For very smooth final polishing, finer diamonds down to perhaps 20 to 30 micron size are sometimes used, the exact size depending on the purpose intended. The boron carbide or other abrasive filler should be finer than the diamonds. It acts partly as a filler to the metal stud and also acts as an abrasive to some degree.

It is desirbale to have the relatively non-abrasive metal base of my stud extend approximately 4; inch along the axis of the stud to permit it to be firmly gripped by cement 4 in the socket cavity 5 in flexible disk 6. The abrasive portion 2 should extend along the axis of the stud a distance of preferably about inch plus 0.01 to 0.02 inch, although this may be varied for different applications.

It is important that all studs project from the disk in which they are set by substantially the same distance, so the next step in assembly of this device is to place each stud in a chuck on a lathe with the abrasive end firmly against an end stop after which the non-abrasive end is turned or ground off to yield studs which are all of exactly the same length before proceeding to mount them as described below.

The stud carrying disk 6 of this device is prepared by providing a round disk from 4 to 8 inches in diameter in one face of which are drilled cylindrical cavities 5 to a precisely uniform depth of approximately A; inch for insertion of the completed stud 1. It is desirable that the bottom of each cavity should be flat and make a right angle with the side Wall of the cavity. This is readily obtained by using a square end drill to finish each hole. I find moreover that it is also desirable to have at the center of each of these holes a further extension hole 7 perhaps /8 inch diameter which extends through the flexible disk 6. This extension hole provides a relief space 3 as the fastening cement 4 is being applied, and any excess of the cement flows into and through the hole. The presence of this relief hole aids in setting the studs so that each one projects equally below the face of the flexible disk 6.

In locating the various holes in disk 6, it is helpful to use a template containing 4; inch diameter holes through which I pass a drill to penetrate through the disk 6 at proper points. This provides the small through holes described and serves to locate the larger cavities for insertion of the studs.

It should be noted that in order to insure proper balance of the final body, these cavities should be located in pairs directly across the axis and arbor hole C from one another and at equal distances from the axis of the disk. It is also important that the cavities be so placed that as the device rotates adjacent studs shall trace paths which overlap to a considerable degree but not completely, to assure uniform polishing and the elimination of grooves and scratches in the stone being polished. I find it desirable that adjacent studs be separated from one another by a distance at least equal to half the diameter of the studs. This means that the working face of the device is relatively open, there being for example only 34 studs of inch diameter each in the entire face of a disk 7 inches in diameter. In this way an important degree of flexibility of the disk under bending loads is assured.

For carrying the abrasive studs in their cavities, I use a disk of a flexible, but not necessarily elastic material, many of which are well known in the art, the only requirement being that at operating speeds the disk will maintain a generally flat, planular posture, yet be capable of flexing in use to accommodate and conform to the contoured surface of the subject sought to be ground. Generally, it can be flexed for up to /2 inch or more with a persons fingers and returns to the flat when released.

As an alternative the abrasive members can be aflixed to the disk by bolts extending through the disk as illustrated in my copending application Ser. No. 640,686 filed May 23, 1967. The nut is buried in the elastomer pad. The resilient grommets employed in said application however are not required in this invention.

The disk is from 7 to inch thick, the inch stock being for disks 6 inches or more in diameter.

The next element in my assembly is a layer of relatively soft elastomer (sponge rubber) material 8. For this inch thick material may be used, and is cut to the same diameter as the disk 6 and as the A inch thick rotatable steel plate 9, to both of which it is cemented by cement 4.

Obviously many suitable springly sponge elastomers or other substances could be used rather than the rubber if desired, and the elastomer may generally be described as a resilient cellular or non-cellular elastomeric body, which shall be understood in the broad sense to include bodies composed of materials having properties similar to those of an elastomeric polymer, at least to the extent that they may readily be elongated at least 300%, and/or compressed at least 50%, by the application of a force of not more than 500 pounds per square inch. It will also be understood that the average diameter of any cells present may generally be of almost any size larger than about 0.01 inch.

In a preferred embodiment of the invention, the steel plate is tapered downward at an angle between about 3 and and preferably between about 4 and about 7 from a point at or near the center of the plate to the outer edge. This taper imparts a slanted working face of about the same amount and causes the polishing wheel to cut more smoothly. The plate is preferably tapered from the circumference of a circle having its center at the center of the plate, the circle having a diameter of between about about 1" and about 2" and preferably about 1%".

Steel plate 9 is positioned on a rotatable shaft by any conventional means, such as threadably, as shown, or may be provided with two diametrically opposed tapped holes 10 in the back face, into which bolts are inserted to hold this plate tight against a shaft plate mechanism (not shown) whereby my entire device is rotatable about its axis.

For holding the various elements of my device together, any of a number of well known, commercially available, flexible, waterproof adhesives may be used.

To assemble the various elements of my device, the first step is to sand blast and wipe off the various faces to be cemented, i.e. studs 1, disk 6 including the cavities therein, and steel plate 9. I then brush onto these surfaces and to both faces of elastomer disk 8 a coating of my cement and allow this to stand in air until it becomes slightly tacky.

Cavities 5 are filled completely with cement before inserting the studs. This insures a complete, firm contact and any excess extrudes away through the vent holes 7 against the elastomer pad 8, where it does no harm.

I then press together the various faces which are to adhere to one another and put the assembled unit under a weight covering it uniformly with a total pressure of about lbs. This I leave on for 20 to 30 minutes after which the Weight is removed and the assembly allowed to set in air in a warm room overnight after which the completed device is ready for use.

FIG. 3 illustrates the ability of this device to conform its working face to that of the stone being polished, for instance across the top of a tomb stone 11. In this figure it will be noted that disk 6 holding studs 1 has flexed to match the curvature of stone 11 but retains its full thickness and continues to grip the studs firmly. Elastomer pad 8 however squeezes down further at area A than at area B where the pressure (applied in the direction of the arrow) is less. Steel member 9 retains its original shape. As the position of the polishing pad is displaced perpendicular to the arrow the shape of elastomer member 8 changes continually to urge abrasive members 2 in contact with the face of the stone.

There are certain limits on the thickness of intermediate elastomer pad 8 and the thickness should be generally less than /2 its total diameter while the lower limit of its thickness is dictated generally by the maximum degree of flexure of flexible disk 6 that will be desired. That is, the thinner the intermediate elastomer pad 8 is, the less permissible flexure of flexible disk 6.

Having thus described and illustrated my invention, it is set forth in the following claims which are to be construed in the light of the United States statutes and decisions in such a manner as to give them the broad range of equivalents to which they are entitled.

What is claimed is:

1. A rotatable abrasive wheel having means to rotate same, said wheel having a generally circular and substan tially rigid base plate fixed directly to said rotating means, an elastomer pad conforming generally to the outlines of said base plate and having one face aflixed thereto, said elastomer pad having aifixed to the opposite face thereof a flexible disk member conforming generally to the outline of said base plate and said pad, said flexible disk member having dispersed over the working face thereof a series of cylindrical cavities of substantially equal depth, said cavities having disposed therein a generally cylindrical abrasive member having an abrasive dispersed over the operating face thereof, said cylinders protruding, respectively, below the working face of said flexible disk, substantially equal distances.

2. The wheel of claim 1 wherein said cylindrical cavities partially penetrate said disk member, and each said cavity has a smaller opening in its base extending through the total thickness of said flexible disk.

3. The wheel of claim 1 wherein said cylindrical cavities partially penetrate said disk member, each said cavity has a smaller opening in its base extending through the total thickness of said flexible disk, and said elastomer pad has a total thickness no greater than half its diameter.

4. A rotatable abrasive wheel having means to rotate same, said wheel having a generally circular tapered base plate, said base plate fixed directly to said rotating means, an elastomer pad conforming generally to the outlines of said base plate and having one face aflixed thereto, said elastomer pad having aflixed to the opposite face thereof a flexible disk member conforming generally to the outline of said base plate and said pad, said flexible disk member having dispersed over the working face thereof a series of cylindrical cavities of substantially equal depth, said cavities having disposed therein a gen 10 6 5. The wheel of claim 4 wherein the base plate is tapered downward at an angle between about 3 and about 10 from a point at or near the center of the plate, to its outer edge.

References Cited UNITED STATES PATENTS 1,953,983 4/1934 Benner 51-395 2,164,418 7/1939 Mounet 51-358 3,121,982 2/1964 Miller 51-209 OTHELL M. SIMPSON, Primary Examiner US. Cl. X.R. 51-209 

